This invention relates to valves generally and more particularly to a valve for diverting fluid flow from a first passage to a second passage. In the prior art valves, fluid flow is often controlled by a diverter vane which is used to selectively seal one passage while opening the other. In these devices, the forces required to switch the diverter from a first to a second position were relatively high since the entire pressure differential between the open and closed passages had to be overcome by a diverter actuator. Additionally, the diverter vane was relied upon for the total sealing of the passage, thus, if a tight seal was required the dimensions of the vane and its mating surface on the passage wall had to be closely controlled in order to insure a proper seal.
In another type of prior art diverting valve, a ball sealing member is used to close one passage and open another. This valve suffers many other of the same deficiencies as the diverter valve described above. High actuator forces were required to move the ball from one passage to the other, since the total differential pressure between the passages had to be overcome by the actuator.
Additionally, in the case of a diverter valve where hot corrosive gases are to be controlled, erosion of the diverter vane can cause excessive leak rates after a given period of use. Thus in hot gas applications the valve life was severely restricted.
The present invention overcomes these disadvantages by combining a diverter valve with a ball valve and utilizing the diverter vane to cause the high pressure of the incoming fluid to move a sealing ball from a first port to a second port. Since the diverter vane actuator must overcome only a small portion of the total inlet pressure, smaller actuating forces are required. Additionally, when the valve diverter is at rest the pressure is substantially equal across its surface thus no force is required to maintain it in a static position. In fact the small pressure differential across the vane acts to maintain it in the closed position. As the diverter is not used for sealing the passage, close dimensional control is not required and erosion of the diverter has little or no effect on the operation of the valve. Thus it can be seen that there is provided herein a valve combining the desirable features of diverter valves and ball valves in a simple device having a long useful life and requiring minimum actuator power.